1. Field of the Invention
The present invention is related to: elevator systems, elevators for wellbore operations, and method of their use.
2. Description of Related Art
Wellbore operations often involve tubulars (e.g. pipe, tubing, and casing) and strings of tubulars which are run into and out of boreholes. Elevators are used in such operations to hold, lift, and lower tubulars.
Several typical prior art elevators have heavy hinged clamps attached to a hook and traveling block by bail-like arms, or “bails”. Elevators often may have one or more doors which close around a tubular. There are single-door and split-door types. One type hinges to open to admit or eject pipe. In hoisting a joint of drill pipe, the elevators are latched onto the pipe just below the tool joint (coupling) which prevents the drill pipe from slipping through the elevator. In lifting casing or tubing, the sections of such tubulars either have an upset end, or they are joined together with an enlarged collar. When the elevator is in a closed position, i.e., when the one or two doors are closed shut, the internal diameter of the elevator is less than the outer diameter of the end of the enlarged tool joint, upset, or collar, preventing the tubular from slipping through the elevator.
In many methods used in handling very large pipe, each section of pipe is picked up from a horizontal or non-vertical position and swung to a vertical position for stabbing into the connection of the assembled tubular string. Certain prior art elevators are placed on the pipe and pivot to orient an elevator throat opening downward with the door or doors swinging on hinge(s). The doors on a large elevator, which must be closed around the pipe, may weigh several hundred pounds. An elevator with door(s) needs clearance for the door(s) to swing in an arc under the pipe being engaged. The pipe has to be elevated, or clearance otherwise provided, for such swinging doors.
“Non-slip” prior art elevators have generally been constructed with doors (generally, one or two) which open to allow the insertion or removal of the tubulars; doors which traditionally are heavy, slow in operation, difficult to handle and can present a considerable safety hazard to the operator. With very heavy tubulars, for example, large casing, the tubular is initially in a horizontal or non-vertical position, laying in place on or near the floor beneath a derrick. The hinged door elevator is lowered near the point of attachment to the tubular. The door or doors, which may weigh several hundred pounds, much then be opened to allow the elevator to be placed over the tubular. Because the door or doors must close around the tubular, the tubular end around which the elevator is located is often above the derrick floor.